| With the gradual transformation of China’s civil engineering industry from largescale new construction to the reinforcement of existing buildings,the reinforcement of existing buildings has become one of the most popular research direction.As a material with good fluidity,micro expansion,rapid development of early strength,and high strength,the application of cementitious grout in the reinforcement of reinforced concrete structures can made up for the shortcomings of traditional concrete–replacement methods,such as long wet working time and difficult concrete pouring and vibration.Compared with the extensive application in engineering reinforcement,the current theoretical research on the reinforcement of existing RC members with cementitious grout is obviously lagging behind,which can not provide theoretical support for the bearing capacity evaluation of RC members strengthened with cementitious grout.This paper systematically carried out research on the stress-strain relations of cementitious grout under compression,the interface bond strength of cementitious grout and concrete substrate,the bond behavior between steel bars and cementitious grout,and the bearing performance of RC members(beams and columns)strengthened with cementitious grout,and the calculation methods of bearing capacity of RC members(beams and columns)strengthened with cementitious grout were established.The specific research contents and results are as follows:(1)The uniaxial compression tests were carried out on cementitious grout specimens,and the variations of stress-strain characteristic parameters(peak stress,peak strain,and elastic modulus)of cementitious grout with different ages were discussed.A segmentbased compressive stress-strain model suitable for cementitious grout was established based on the test results.(2)The interfacial bond performance tests of cementitious grout-concrete were carried out on splitting tensile specimens and slant shear specimens,and the effects of concrete substrate strength and surface roughness on the failure mode and interfacial bond strength of splitting tensile and slant shear specimens was analyzed.Moreover,the calculation models of interfacial bond strength between cementitious grout and concrete were proposed.(3)The pull-out tests were carried out on cementitious grout pull-out specimens,and the effects of specimen age,reinforcement diameter and cover thickness on failure modes of specimens,bond strength,peak slip and shape parameters of bond stress-slip curves were analyzed.The bond strength model and bond stress-slip constitutive relationships between the cementitious grout and deformed steel bars were established.(4)8 existing RC flexural beams and 24 existing RC shear beams strengthened by replacement with cementitious grout were designed and manufactured for test,and the effects of reinforcement position,reinforcement layer thickness,shear span ratio and other parameters on the flexural and shear behavior of the strengthened specimens were analyzed.Calculation methods of flexural capacity and midspan deflection of RC beams strengthened with cementitious grout were established by considering the effects of reinforcement position and reinforcement thickness.Moreover,a calculation method of shear capacity of RC beams strengthened by replacement with cementitious grout is proposed based on the truss-arch model.(5)12 existing RC axial compression columns and 16 existing RC eccentric compression columns strengthened by replacement with cementitious grout were designed and manufactured for test,and the effects of reinforcement position,reinforcement thickness,eccentricity and other factors on the axial compression performance and eccentric compression performance of the strengthened columns were analyzed.Considering the lateral restraint of stirrups,the cooperative work of cementitious grout and concrete,and the influence of physical eccentricity caused by asymmetric reinforcement,a calculation method for the axial compression capacity of existing RC columns strengthened by cementitious grout was established.Meanwhile,the calculation method of bearing capacity and deformation of existing RC eccentric compression columns strengthened with cementitious grout were also proposed by considering the effects of reinforcement position,reinforcement thickness,and eccentricity. |
